1. Field of the Invention
The present invention relates to an information recording apparatus wherein recording irregularities caused by fluctuations in the moving speed of an image forming member are corrected.
2. Description of the Prior Art
In one type of information recording system, electrical information signals are converted into an optical image through a scanning reproducing device such as an optical fiber tube, a thin wall tube (TWT), or a laser beam scanning device. This optical image is projected onto a photosensitive substance to form thereon an electrostatic latent image which is then processed in an electrophotographic manner to be recorded on a recording sheet. In another type of system, electrical information signals are impressed on an electrostatic recording needle such that an electric discharge takes place between the needle and a dielectric substance on which an electrostatic latent image is thereby formed; this latent image is then electrophotographically processed to be recorded on a recording sheet.
In apparatus of each of these types, an electrostatic latent image forming means (such as an optical fiber tube or an electrostatic recording needle) is placed in facing relation to an image forming member (such as a photosensitive or a dielectric substance), the image forming member being usually carried on the surface of a drum arranged for constant speed rotation in one direction. The electrostatic latent image forming means electronically scans along the drum surface in the widthwise direction of the recording sheet while the image forming member is mechanically moved in the advancing direction of the recording sheet, whereby an electrostatic latent image corresponding to electrical information input to the image forming means is impressed onto the image forming member.
The revolving drum is generally rotated by a driving mechanism having a motor as a driving source. In use, fluctuations in the drum revolving speed sometimes occur, being caused by variations in the frequency of the power source, or by abrasion of the driving mechanism, or manufacturing error, resulting in irregular drum movement. The electrical information signals input to the image forming means, on the other hand, are generated at regular, predetermined intervals (in accordance with clock signals); thus, irregular movement of the image forming member negatively affects the recorded image and prevents attainment of a properly recorded image.
By way of example, for an information recording apparatus wherein characters are recorded on a sheet of regular size (such as A4, B4 or B5) in accordance with electrical information signals, 30 lines of character information can be recorded within a predetermined frame or area on A4 size paper using a certain moving speed of the image forming member. However, with fluctuations of the speed of the image forming member, 30 lines can not be included in the desired frame; depending upon the magnitude of speed changes, or when the fluctuations are extremely large, it happens that only 29 lines can be recorded. This situation not only detracts from the outward appearance of the recorded material but also results in missing information such that the information that has been recorded becomes useless. Furthermore, in a recording apparatus wherein a dot-matrix system is employed for character generation, fluctuations in the moving speed of the image forming member produce recorded characters that are distorted as well as uneven or rugged spacing between lines of recorded characters.